Handling KeyError exception on dicom_reader to dicom with nonstandard encoding

Some dicom files have encoding names that do not follow the standard, in
these cases a default dicom encoding (ISO_IR 100) is used.
Using replace method error to decode dicom fields and avoid crashes.

Some dicom files have the encoding setted wrongly, so when decoding a
dicom field from string to unicode some errors may happen. Python string.decode
have some methods to handle those cases. We are using the "replace" one,
the characters it cannot decode to unicode it replaces with a character
showing the character was not decoded.
FIX: It was not possible to export 2d slice screenshots

it was because of AttributeError related to renderer.
Set ImageType to empty when there is not this tag in dicom
Updated the shebang python path to /usr/bin/python
Removed execution permission (unix) from some files
Renamed LICENSE-pt.txt to LICENSE.pt.txt
Converted LICENSE.pt.txt from latin1 to uft-8
Sample2 was removed because it's in the old invesalius project file format
styles.SetOrientation was without a function body
Updating threshold presets limits when opening a dicom, analyze or inv3 file
Not closing InVesalius when closing the project
Making possible to use Ctrl+q to close InVesalius
InVesalius was not exiting when closed via menu/close
Not using thread anymore to write session file
Only checking for update if invesalius/config.cfg has a id_random
It's not necessary to sys.exit in onclose
Updated the INVESALIUS_VERSION to beta4
Updated to beta4 in about dialog
FIX: Fixed ReadBlue stereo on Windows