[Setup] Add choice to add install dir to PATH

Git Extensions' installation directory will be added to the system
environment variable "PATH" if selected. Defaults to yes.
Always add to the _system_ variable and not user variable, since
the install package can't install without administrative privileges
anyway, so the "install for this user only" option is broken anyway.

The directory will be removed from PATH when Git Extensions
is uninstalled.

Solves issue #438 (which is a feature request).
Localization files updated
update french translation
update changed string too
adjustments...
Little reduction of 'command' text input in the ScriptsSettingsPage to prevent broken GUI

The 'Browse' button fall behind the textarea in different translation (french, dutch, russian,...)
Merge pull request #2037 from pmiossec/french_translation

Update french translation for v2.47
Correct displaying state of the 'Show progress' option in script options
Json Serialization for 'Commit templates' + migrate datas!
Merge branch 'pr/n2024_HenrikTorstensson'
TranslationApp manifest fixed
Russian translation updated
<OldSource> tag removed from Francais.xml, because translation was updated
TranslationApp now can hide translated categories and show unfinished translation
Minor translation files updates
Merge pull request #2041 from pmiossec/correct_show_progress_checkbox_state

[v2.47] Correct show progress checkbox state
ShowProgress default to true.
Merge branch 'pr/n2043_pmiossec' into release/2.47
Serialize and deserialize using the same encoding.
Remove unused code