Add show_cache_statistics command with raw output

The new show_cache_statistics command just shows the response gotten
from the runtime when calling cache_statistics using pretty print.

It can be like this:

{u'totals': {u'Module.Entity': 116,
             u'Module.Entity2': 4},
 u'user_totals': [{u'amounts_per_type': {u'Module.Entity': 116,
                                         u'Module.Entity2': 4},
                   u'disk_count': 0,
                   u'memory_count': 120,
                   u'total_count': 120,
                   u'user_name': u'unknown'}]}

By the way: unknown is not the user unknown, I guess it's the runtime
'system session'. Dunno what happens when I actually have a user with
username 'unknown' in my application. I guess I get duplicate output,
where the user and system cache is indistinguishable from each other.

I have no idea yet about how to properly format this output. There's
three levels of detail:
 1. totals (they're also in the output of the general runtime_statistics call)
 2. totals, breakdown by entity
 3. totals, breakdown by user session and entity

Possibly we can use an argument to the show_cache_statistics command,
like:
 - show_cache_statistics totals -> shows total total amount and the
   breakdown per entity, and tell the user to do show_cache_statistics
   user if it wants to see breakdown per user session (default)
 - show_cache_statistics user -> shows breakdown per user session
refactor appcontainer class name if hybrid

use the public method to detect hybrid, which name explains what it is doing
warn about obsolete or missing constants

Often m2ee.yaml is not cleaned up after a new release that scraps a
constant. This leads to a cluttered m2ee.yaml. Also it would be nice if
m2ee warned about missing constants directly when unpacking instead of
on startup.
cosmetic: nicer output of missing/obsolete constant warnings
Experimental show_cache_statistics_raw for now

Remove this one when the pretty version, show_cache_statistics is
implemented.
Merge branch 'more_cache' into develop
Merge remote-tracking branch 'origin/sync-constants' into develop
Prettify debug printing of environment at start

...so it's easier to copy-paste it on the command line when you want to
debug the runtime and start without putting the process in the
background.