Decode

+ `plot_chmap` now returns mappable and does not plot colorbar inside it
+ Delete default styles of xlabel, ylabel, and title of plot functions
+ Fix `plot_timestream` (before that an error occurs when plotting)

Removed
+ `dc.models.skewgauss()`
+ `dc.models.r_subtraction()`
+ `dc.models.savgol_filter()`
+ `dc.models.rsky_calibration()`
+ `dc.plot.plotweather()`

Implemented
+ `dc.models.gauss_fit()` made by Koyo
+ `dc.fromcube()` made by Akio
+ `dc.plot.plot_chmap()` made by Tsuyoshi

Updated
+ `plotcoords()` => `plot_tcoords()` (backward compatibility has been held)
+ `plottimestream()` => `plot_timestream()` (**backward compatibility has been lost**)
+ `plotspectrum()` => `plot_spectrum()` (backward compatibility has been held)
+ `savefits()`
- casaviewer has been supported
- still should be upgraded

Miscellaneous
+ implemented `deprecation_warning` decorator
+ changed some of the internal structures
+ made the logger fucntions a standard way

This release fixed the following bugs:

1. [creation of default scantype](https://github.com/deshima-dev/decode/commit/953bd5ac749803cd4033f3b85e5c4c3a4fd2d84c)
2. [invalid function name](https://github.com/deshima-dev/decode/commit/f37ef88197679bcac56e05a3d3fb2a6fac0e0495)

array function
dc.concat
+ [**Bug Fixed**] `xref` and `yref` of the concatenated array is adjusted to the 1st array.

i/o function
dc.io.loaddfits
+ A new keyword of `shuttle` is implemented for shuttle observations. When this is True, x coordinates of off-point and on-point are specified via keywords of `xmin_off`, `xmax_off`, `xmin_on`, and `xmax_on`.

model funtion
+ **Calculation speed gets much faster!**
dc.models.chopper_calibration
+ A new calibration method has been implemented. This can be used in the same way as dc.models.rsky_calibration.
python
dc.models.chopper_calibration(onarray, offarray, rarray, Tamb, mode='mean')

plot function
dc.plot.plotpsd
+ PSD plot.
python
plotpsd(data, dt, ndivide=1, window=hanning, overlap_half=False, ax=None, **kwargs)


dc.plot.allanvar
+ Allan variance plot.
python
plotallanvar(data, dt, tmax=10, ax=None, **kwargs)


cube function
dc.makecontinuum
+ Values of channel coordinates of the continuum (`masterid`, `kidid`, `kidtp`, and `kidfq`) have been changed.

dc.savefits
+ [**Bug Fixed**] The header for the az/el data has been corrected.

i/o function
dc.io.loaddfits
+ A kwargs of `findR` has been implemented. When this is True, loaddfits will automatically find R positions according to some user-defined parameters. `Rth` is the threshold above which data will be categorized as R, and `skyth` is the threshold below which data will be categorized as SKY. This calculation depends on one representative channel, which specified via a keyword of `ch`. `cutnum` determines the number of data points which will be not used at the edges.
+ A kwargs of `still` has been implemented. When this is True, loaddfits will change scantypes to SCAN and OFF. The cycle is specified via a keyword of `period`.

model function
dc.models.pca
+ [**Bug Fixed**] [**IMPORTANT**] The implementation of PCA had problems, but the bugs are removed.
+ None can be used as `mode`.

dc.models.r_subtraction
+ Apply R-subtraction.
python
dc.models.r_subtraction(onarray, offarray, rarray, mode='mean')


dc.models.r_division
+ Apply R-subtraction.
python
dc.models.r_division(onarray, offarray, rarray, mode='mean')


utils
dc.utils.psd
+ Calculate PSD.
python
dc.utils.psd(data, dt, ndivide=1, window=hanning, overlap_half=False)


dc.utils.allan_variance
+ Calculate Allan variance.
python
allan_variance(data, dt, tmax=10)