Cleanup data files installation

Don't use wildcards to select files to install, nor manually perform
the installation when Automake could do it for us.

Using wildcards makes it hard to know what will really be installed,
and may results in installing files not part of the distribution.
Cleanup documentation files installation

Don't use wildcards to select files to install, nor manually perform
the installation when Automake could do it for us.
Unify encoding combo boxes

Make all encoding combo box display a list with encodings grouped by
categories into sub-menus, making it easier to find the appropriate
encoding than in a big single-level list.

This is what was used in the Open dialog, but not in the Preferences
dialog or the Find in Files dialog.  This also makes the encoding
combo boxes behave more like the encoding menus.
Group filetypes in the Open dialog filetype combo box

Display the filetypes in the Open dialog filetype combo box grouped,
as they are in the filetypes menu.

This makes it easier to select a filetype, because they are better
sorted and follows the filetypes menu layout.
Merge branch 'unified-encoding-combo-boxes'
Merge branch 'cleaner-filetype-combo-box'
Add a translation context to the open dialog's "View" button

The "View" button string is the same as the View menu one, but one is
an action (verb) and the other a noun, and as such might need to be
translated differently.
Reword "Detect from file extension" from the open dialog

We don't actually detect from file extension only, and other references
of the feature always use "Detect from file", so use it also in the
open dialog.
Small update of the French translation