JSON parser fixes and new testcases

Addresses point 1 and 2 in #563 but left 3 due to the risk of
regression.
Merge pull request #589 from ovatsus/master

Finish Xml write API
Merge pull request #595 from ovatsus/master

Fix disposing of file system watchers (closes #590)
Merge pull request #594 from mrange/master

JSON parser fixes and new testcases
Update release notes
Test for #591