[ADD] WebDAV: initial implementation
- added classes for handling collection databases and ordinary folders
[MOD] WebDAV: Implemented create, delete and export of databases.
Merge branch 'webdav' of github.com:dimitarp/basex-api into webdav

Conflicts:
	src/main/java/org/basex/api/webdav/BXAllDatabasesResource.java
	src/main/java/org/basex/api/webdav/BXResourceFactory.java
Renaming:
- BXDatabaseCollection -> BXCollectionDatabase
- BXDocumentResource -> BXDocumentDatabase
New:
- created BXDocument for handling documents which are part of
collection databases; BXDocumentDatabase represents a database
consisting of a single document
[MOD] WebDAV: fixed class path
[MOD] WebDAV: refactoring + some fixes
[MOD] WebDAV: refactoring
Fix for displaying xml documents in a collection db
Merge branch 'webdav' of github.com:dimitarp/basex-api into webdav

Conflicts:
	src/main/java/org/basex/api/webdav/BXFolder.java
Added logic for displaying documents in a collection db
[MOD] WebDAV: fixed coding warnings
[MOD] WebDAV: added BXDatabase class
Merge branch 'master' of github.com:BaseXdb/basex-api into webdav
Merge branch 'master' of github.com:BaseXdb/basex-api into webdav
[MOD] WebDAV: using client session
Merge branch 'webdav' of github.com:dimitarp/basex-api into webdav

Conflicts:
	src/main/java/org/basex/api/webdav/BXAllDatabasesResource.java
	src/main/java/org/basex/api/webdav/BXCollectionDatabase.java
	src/main/java/org/basex/api/webdav/BXDocumentDatabase.java
	src/main/java/org/basex/api/webdav/BXResource.java
	src/main/java/org/basex/api/webdav/BXResourceFactory.java
[MOD] WebDAV: user credentials in the resouce factory
[MOD] WebDAV: user credentials in resource factory
[MOD] Modified methods getChildren() of BXFolder and
BXCollectionDatabase to use XQuery for children retrieval
[MOD] Modified getResource() method of BXResourceFactory to create
different types of BXResource depending on the path