remove duplicate of code (cleanup is already done later in nicer way)
Only set display if it was previously defined into the function call (i.e. request) otherwise
this leads to a difference between generated cache id for set and get for *same* function call
thus eliminating image caching.
Examples of generated cache ids:
(get) -> 39600:5:formatpngquality45.0
(set) -> 39600:5:displayNoneformatpngquality45.0
Formulator: clean up FloatWidget.format_value
TestFloatField: fix test_render_big_numbers on Python 2.7
safe_html: fix handling of broken html on Python 2.7

Also simplify sample HTML in test_safeHTML_conversion
Fix testWebDavSupport on Zope 2.13
Fix testArchive & testERP5Catalog on Zope 2.13
Fix _set*UidSet accessors
CategoryTool: clean up getCategoryParentUidList
CategoryTool._setCategoryMemberShip: bugfixes and cleanup

- duplicated default categories were dropped when the list of categories was
  passed without their base categories
- accept any iterable for 'category_list'
CategoryTool: remove ancient _cleanupCategories migration method
CategoryTool.getAcquiredCategoryList: do not duplicate loopback value on categories
CategoryTool: optimize getCategoryList and getAcquiredCategoryList
CategoryTool: remove broken/unused getRelatedValueList parameters
Reset cache listing categories for ZSQLCatalog when base categories are edited
testCMFCategory: clean up afterSetUp
CMFCategory: add support for ZODB indexing of related documents
Do not display login user reference by default
Check that the reference input by user is not already defined in acl-users folders
filter dependency even when install-depencency is True

This must prevent the useless download of bt5 which are already installed
And so this is supposed to reduced the number of bt5 installed by configurator and make it faster