XWIKI-10608 use getXWikiPreference('admin_email') if it is filled

http://jira.xwiki.org/browse/XWIKI-10608
XWIKI-10665: ## characters displayed in info box when resetting a lost password
+ Use the new mail sender API
[cleanup] Applied codestyle
[misc] Fixed integration tests: removed the -f flag, since instead of specifying a file, it disables shell globs
[misc] Set the most common relative path to the parent project to avoid Maven warnings
[cleanup] Applied codestyle
[misc] Applied codestyle
XWIKI-10666: Custom displayer for emails should generate HTML
XWIKI-10670: Make job UI displayer toolkit usable outside of extension module
XWIKI-10669: Make log UI displayer toolkit usable outside of extension module
XWIKI-10655: Display XWiki initialization job log if anything goes wrong
XWIKI-10655: Display XWiki initialization job log if anything goes wrong
* minor improvement
XWIKI-10655: Display XWiki initialization job log if anything goes wrong
XWIKI-10655: Display XWiki initialization job log if anything goes wrong
XWIKI-10655: Display XWiki initialization job log if anything goes wrong
XWIKI-10655: Display XWiki initialization job log if anything goes wrong
XWIKI-10655: Display XWiki initialization job log if anything goes wrong
[misc] Apply codestyle
Provide API to programmatically flush rendering cache from components for specified document.
[misc] Fix warning
XWIKI-10673: When importing a XAR with "import as backup pack" the creation date is current date
XCOMMONS-620: Move WikiStream generic part to commons filter