Added base64 in digest module
* Removed b64decode from box_net_box.lua
* Added base64_encode() and base64_decode() methods in digest
* Added base64 tests
Fix base64 endcode/decode sizes, and added more tests
Merge remote-tracking branch 'origin/gh-367-add-module-base64'
Update test results.

Restore OOM test (TreeIndex moved to another arena).
Update digest.result (spaces)
Update net.box.result (line numbers).