Relax limits on size and update frequency

The current size and frequency limits appear arbitrary. Some users might want a higher update frequency and/or larger size of the plot. This patch grants them. 100ms is the new lower bound. I understand that lower values might eat up the CPU. The user should realize this latest by looking at the plot itself..
Reset statistics widget only when size changes. Fixes lxde/lxde-qt#353
Commit from LXDE Pootle server by user H.Humpel.: 124 of 305 strings translated (0 need review).
Panel background configuration

Options to set background color and/or image
Custom font color handling. Fixes #101.
Make the lxqtmount-qt5 required only when building the mount plugin.

It was always required. Closes lxde#363.
Reorganize panel configuration dialog
Renames the translations source files

Renames it from xxxxx.ts.src to xxxxx.ts
Uses the new translations cmake modules
Moves translations from the local to the translations dir

We don't look there anymore.
Fixes translations generation

Closes lxde/lxqt-panel#367.
Fix draggind action from main menu
Get rid of Xlib on the keyboard indicator

Done using KGuiAddons's KModifierInfo
More info: http://api.kde.org/frameworks-api/frameworks5-apidocs/kguiaddons/html/classKModifierKeyInfo.html