Exit expirer earlier if db-ttl is disabled

Now, the ceilometer-expirer exit without doing the backend db request if
the db-ttl is disabled.

Fixes bug #1270760

Change-Id: I49580be14cd932317ff30070aeec391ef456712e
Set the SQL Float precision

By default mysql use a precision of 23 to store a Float and
sqlite/postgresql use 53.

The patch set the precision of Float to 53 to force all sql backends to
use the same double precision.

Change-Id: I36680ed180999e401e45428af068fd32126247da
StringIO compatibility for python3

StringIO can be replaced with six.moves.StringIO which can provide
compatibility for Python 2 and 3. So does cStringIO.

Change-Id: Ieed1e97f1832e56717bc905114eb73fd6c4c4d04
Fix the Alarm documentation of Web API V2

Correct the Alarm example on the API documentation to contain a
valid Alarm sample and complete the Note section with information
about the connection between the type and rules fields of the
Alarm.

Fixes bug #1245362

Change-Id: Id7209d3f7a7ab29a50bdb1dfbe90937b1c7c6c8d
Move enable_acl and debug config to ceilometer.conf

These user editable config params are moved from
pecan config to ceilometer.conf

Change-Id: I8686987e5d92e38e2a9cfbd3f35eea0cc2b443c5
Closes-bug: #1256111
Exclude weak datapoints from alarm threshold evaluation

Addresses: BP exclude-low-sample-count

To avoid alarm threshold evaluation being inappropriately skewed by
aggregates with anomalously low sample count, these weak data may be
excluded for selected alarms by setting a new 'exclude_outliers'
field on the alarm threshold rule.

An outlier in this context is considered to be an aggregate with
sample count that differs from the observed mean by more than two
standard deviations.

Change-Id: I45d05db57662588df5796a8d6864ed01d1e4165f
Merge "Set the SQL Float precision"
Merge "Exit expirer earlier if db-ttl is disabled"
Merge "Exclude weak datapoints from alarm threshold evaluation"
Merge "Move enable_acl and debug config to ceilometer.conf"
Merge "Fix the Alarm documentation of Web API V2"
Merge "StringIO compatibility for python3"