fix exception in IndexUpdaterTest
remove objects from fullText index field
add html2PlainText parser for content field
Merge branch 'stable-2.7.2' of github.com:celements/xwiki-platform-search-lucene into stable-2.7.2

Conflicts:
	src/test/java/com/xpn/xwiki/plugin/lucene/IndexUpdaterTest.java