Optimize access to timezones (instead of TimeZone#getTimeZone)

As seen with NXI-2 TimeZone#getTimeZone uses synchronized blocks that can lead to thread locks.

For now we have fixed this in the nuxeo-drive code with a static constant as Drive sends many queries that were using this blocking code, see NXP-15891.

Yet we should chek all occurrences of TimeZone#getTimeZone in the nuxeo code base to refactor it maybe using joda-time that handles timezone properly.
Main places are:

• SchemaManager
• Automation JSON serialization
• CMIS
• APIDoc

And let's also refactor the Drive quick fix done for NXP-15891.

Note that Java 8 is supposed to handle timezone properly, so we should check this when we switch to Java 8.