#JC-1869 Try to combine plugin and system permissions

Aim is a processing system and plugin permissions as one collection.
Permissions are loaded on the page, but for plugin permissions editing
is disabled because AdministrationController work with BranchPermission
only. Need to have method for finding by mask for system and plugin
permissions.
#JC-1869:Questions permissions

*Avoided generic permissions everywhere where possible. Now we use JtalksPermission interface instead of it

*Added custom Jcommune permission factory to process standart and plugin permissions

Added plugin permissions factory to process plugin permissions

*Now permissions from plugins can be listed and changed via edit permissions dialog

Corrected unit tests

Seems like some refactoring will be needed
#JC-1869:Questions permissions:
*Fixed mistake with loading non-enabled plugins
*PluginPermissionFactory now initialize only one time
#JC-1869:Questions permissions:
*Plugin logic replaced into separated module
*Added NullPermission to handle permission from removed plugins
[JC-1822][JC-1874] Correction of untranslated english messages in
Spanish properties. Maintenance of the spanish properties with new
additions. Modification of the entrance label.login_error in all
languages according to the given texts in [JC-1874].
JC-1874 Fixed typos in login error labels

Additionally removed dots from the end of each message, they seem
to be odd.
Merge branch 'master' of github.com:jtalks-org/jcommune
#JC-1841: Edit branch permissions:
*Added TopicPlugin interface
*Now question button can be shown if appropriate permission
is granted
TODO: Refactoring, tests, documentation, remarks
#JC-1869:Questions permissions:
*Rewrote PluginsPermission factory. Now it not caches plugin permissions. It always returns actual state.
 *Interface PluginWithPermissions renamed into PluginWithBranchPermissions because, I think, there is no sense to have so common interface in current step (If plugin will work with all 3 kinds of permissions may sense to split it into separate plugins).
*Removed handling general and profile permissions for plugin to prevent premature complication
*Corrected NullPermission enum: removed unused properties
#JC-1869:Questions permissions:
*Corrected all pom.xml files. Now there is correct indentations in them
 *All pom.xml files now use ${project.gtoupId} instead of org.jtalks.jcommune
#JC-1869 Questions permission

Rename branch permission for questions-n-answers plugin
#JC-1869:Questions permissions:
*Unit tests added
*PluginManager renamed into PluginPermissionManager
#JC-1869:Questions permissions:
*Added documentation
Merge branch 'master' of github.com:jtalks-org/jcommune

Conflicts:
	jcommune-plugins/questions-n-answers-plugin/src/main/java/org/jtalks/jcommune/plugin/questionsandanswers/QuestionsAndAnswersPlugin.java
#JC-1841: Edit branch permissions:
*Corrected properties encoding
*Package or.jcommune.plugin.api.plugin renamed into org.jcommune.plugin.api.core
*Corrected remarks from github
#JC-1841: Edit branch permissions:
*Label internationalization
JC-1869 Got rid of duplications in plugins pom.xml

Moved out the configuration of the plugins into plugins' Plugins Parent POM
into `<pluginManagement>` and simply referring to this configuration from
sub-modules.

Additionally moved out properties, distributionManagement and repositories
to Plugins Parent POM.
JC-1869 Got rid of warnings and added javadocs to QnA plugin
#JC-1869:Questions permissions:
*Plugin internationalization placed into plugin itself
#JC-1869:Questions permissions:
*Corrected tooltips