debian: adding libfm-modules into Depends for lxpanel.

The module "vfs:menu" is required for plugins to work correctly.
.gitignore xml-purge nomore!
debian: add libxml2-dev into build-deps (weather plugin require it)
Fix compilation warning about panel_draw_label_text() args.
Add few convenient macros config_group_* for easy group members add.
A little bit more readablility for src/configurator.c.
Create desktop entry if launchbar button was defined manually without id.

If user has created a button using keys 'action', 'tooltip', etc. then on
migration to new launchbar plugin he/she may lose that button.
The commit adds creation of application desktop entry for specified button
and then write back its id so button will be available still.
Add symlink to src so plugins may use '#include <lxpanel/plugin.h>' statement.
Migrate loadable plugin "cpu" to new modules API.
Fix compilation warnings in plugin "cpu".
src/configurator.c: name functions more obviously
src/conf.c: clarify code, save some duplication
Remove unused variables.
Add mandatory checks into callbacks that used in g_source_remove().

If source is removed the most probably its data are freed so
running any job should be prohibited.
Minor updates to .gitignore and weather plugin Makefile.am.
Merge branch 'master' of git://lxde.git.sourceforge.net/gitroot/lxde/lxpanel