Read filetype's mime type from the configuration files

This allows custom filetypes to define a mime type, hence the icon
displayed for this filetype;  as well as moving ones for built-in
filetypes out of the code to the configuration files.
Use GIcon for the filetype icon rather than rendered pixbuf

This allows to re-use the icon more easily since it's not rendered at
a particular size but simply an icon description.  It also allows for
implicit icon updating when the theme changes if the display code
implements it (and GTK widgets does).
Update the HACKING file, explain PR

Add the new way of contributing for geany.
Typo corrections for German language file.
Merge pull request #232 from stefan-it/enhancement/lang-de-corrections

Typo corrections for German language file.
Updated Hebrew translation
Update of German translation
Merge pull request #224 from bestel74/update_HACKING_file

Update the HACKING file: add "pull request" before "patches"
Fix restructuredText syntax
Update zh_CN.po
Update zh_CN.po
Add the choice to use Windows or Gtk color chooser dialog

Modification of the string "Use Windows File Open/Save dialogs" to
"Use Windows native dialogs".

Signed-off-by: bestel <steven.valsesia@gmail.com>
Signed-off-by: Colomban Wendling <ban@herbesfolles.org>
Update of po files for string freeze of Geany 1.24
Update of German translation
Update NEWS files for more updated translations
Updated Czech translation
Update of Spnaish translation
Update NEWS files for more updated translations
Update zh_CN.po
Merge pull request #235 from xhacker/zh_CN

Update zh_CN.po