Translation feedback - Add contextual marker for short strings

This commit add contextual markers to some short strings
which turned out difficult to distinguish during translations.

The detail descriptions are available in the bug report.
Closes-Bug: #1367104

Change-Id: I5ec2045b12542c8474356023bed73d583dc8dccd
Reuse API client object in a request

Previously API client object like novaclient are created
every time methods in openstack_dashboard/api.
It leads to regeneration of API HTTP connections.
This commit caches API client object for a WSGI request
to reduce the number of HTTP connection to backends.
As WSGI request object is recreated, a cached API client
object will live in a single request to Horizon.

Change-Id: I66620b3b0a2737c7232d91006e65d0fabbd3090b
Closes-Bug: #1352144
Uniquify horizon messages returned in a single response

A network operation can fail because of different
reasons - yet in many places just one error message
is provided. Combined with too broad exception clause,
and incorrect assumptions on the reasons of failure
(e.g. Neutron service being unavailable causes all
other sorts of errors like inability to Allocate IP
or Associate it) this leads to multiple errors when just one
would suffice. The fix aims to provide sensible error
messages in case the network service is down. This includes
returning only unique messages in a single response.

Partial-Bug: #1301374
Change-Id: Id6c620ca51f7703f35c0c172e39fdf237fa42278
Co-Authored-By: Timur Sufiev <tsufiev@mirantis.com>
Removing obsolete reference to lesscpy

The settings file still contains a COMPRESS_PRECOMPILER reference
to lesscpy. With the transition to pyscss, this is no longer
necessary.

Closes-Bug: #1370823
Change-Id: I3baf70a631ef4560570c47d0982c8bc4ee3f8412
Imported Translations from Transifex

Change-Id: Ie67e020fa700a193158774d0f83fa4b025fad825
Merge "Uniquify horizon messages returned in a single response"
Merge "Removing obsolete reference to lesscpy"
Merge "Translation feedback - Add contextual marker for short strings"
Merge "Reuse API client object in a request"
Merge "Imported Translations from Transifex"
Merge branch 'master' of https://github.com/openstack/horizon