Asammdf

Fixes
* fix attribute error in MF4 class

Fixes
* fixes 279, 281
* support channel arrays with conversions
* fix for look-up channel arrays with no samples
* fix MDF.select when it is called with record_count!=None
* fix for displaying channel information in GUi for MDF v3 measurements
* fix Tabular window in case of string channels
* fix extract_can_logging and extract_can_signal when the payload size is smaller than the message DLC found in the CAN database
* set the actual record count in the yielded data of _load_data
* fix functionality related to the "Filter" tab in the GUI

Changes
* added _iter_to_dataframe_ method
* added _\_\_lt\_\__ special method to the MDF class to allow sorting of measurement files based on the header timestamp
* add initial implementation for visualizing channel from multiple files in the same plot

Changes
* delay the creation of the filter tree so improve file load time in the GUI
* do not populate the raster channel combobox until the resample tab is selected to dramatically improve the loading time

Fixes
* fixes 277
* fix error caused when the last data block is bigger then the size that is need to hold the required channel groups cycles


Changes
* add copy_on_get keyword argument to MFD class
* improve initial plot loading time

Changes
* add copy to clipboard button to error dialog