Pyjams

* Added module `datetime` with class `datetime` that mimics cftime.datetime
but for non-CF-conform calendars. It also adds the functions `date2num`
and `num2date` for conversion between datetime objects or string
representations and numerical times. It adds the convenience wrappers
`date2dec` and `dec2date` for easier portability of older code using
JAMS.
* Allows more usage of helper functions `input2array` and `array2input`
by allowing undef=None in and making it the default.
* Make netCDF4 an requirement of ``pyjams``.
* Use I/O type helpers in `str2tex`.
* Use I/O type helpers in `date2date`.
* Allow strings and string arrays in `array2input` and `input2array`.
* Add kwargs mechanism to `plot_save` in `mcPlot` to pass arguments
to save_file.
* Add --transparent as a standard option in `mcPlot`.

* Added module `ncio` with netCDF4 functions to copy netcdf files while
doing some transformations on variables and dimensions.
* Added shape keyword to `infonetcdf`.
* Assert that at least one of nc, snc, cname, or sname is given in call to
`xread`.
* Change from NCL amwg to pyjams amwg as the default color palette in
`mcPlot`.

* Added `pyjams_amwg` color map.
* Bandwidth h output of `kernel_regression_h` is scalar if one-dimensional.
* undef=np.nan is default in helper functions `array2input` and
`input2array`.
* Array masked or set to undef only if shapes of array and input agree in
`array2input`.
* Output of `kernel_regression` now has the type of `y` and not `x` or
`xout`.
* `get_color` can get list of colors and not only single colors.
* Register ufz colors only once with `get_color`.
* Add `print_colors` to print known named colors to console.

* Add `gridcellarea` to calculate the area of grid cells on Earth in
square metre.
* Add `kernel_regression` and `kernel_regression_h` for multi-dimensional
non-parametric kernel regression.

* Add `infonetcdf` and `readnetcdf` to get variables from or print
information of a netcdf file.
* Add `get_color` to get value of named colors known to Matplotlib.
* Added named colors of the guidelines of the Helmholtz Centre for
Environmental Research - UFZ, Leipzig, Germany.

* Use `array2input` and `input2array` in `division`, correcting bug with
scalar input and getting rid of numpy geterr and seterr.
* Enhanced `array2input` to take second input variable.
* Added functions `isundef` in `helper` module to deal with NaN and Inf.
* Added 'order' keyword to `get_cmap`.
* Added functions `array2input` and `input2array` in new `helper` module to
assure same input and output types. Use them in `esat` and
`alpha_equ_h2o`. The `helper` module is not in `__init__.py` nor in the
documentation (yet?).
* Return numpy array if type(input)(output) fails for unknown iterable
types in `esat` and `alpha_equ_h2o`.