[#1403] Send 500 on null headers

Strips out the body as well and log debug
[#1845] Implement Constraints.email
[#805] Fix i18n of form fields
Added test for JavaAsync doc's controller method signature
[#805] Fix documentation
Merge pull request #1896 from richdougherty/async-docs-test

Added test for JavaAsync doc's controller method signature
Merge pull request #1894 from baloo/improvements/1845-contraints-emailvalidator

[#1845] Implement Constraints.email
Merge pull request #1895 from baloo/defects/805-helpers-repeat

[#805] Fix i18n of form fields
Upgrade guava
Upgrade to the final bonecp 0.8.0 release given a number of bugs that it repairs - including problems around re-using prepared statements.
Merge pull request #1900 from benmccann/guava2

Upgrade guava
Merge pull request #1876 from baloo/bugfixes/1403-header-null

[#1403] Send 500 on null headers
Merge remote-tracking branch: upstream/master