Simplify filtering by enum columns

[dmitrykuzmin]

This PR simplifies the process of creation of the enum column filters.

It's currently required for all enum column values to be wrapped as Protobuf EnumValue before being passed to the filter, to enable the correct processing on the server side.

Previously, creating such a filter required verbose and hacky code on the client side.

This PR extends the client API so now such filter can be created as follows:

import {enumValueOf, Filters} from '.../client/actor-request-factory';

const filter = Filters.eq('task_priority', enumValueOf(Task.Priority.HIGH));

Spine version advances to 1.2.10.

[dmitrykuzmin]

@armiol PTAL.

The build depends on base#501 and core-java#1215.

[dmitrykuzmin]

@dmdashenkov PTAL.

[dmdashenkov]

LGTM as soon as the build passes.

[codecov]

Codecov Report

Merging #127 into master will decrease coverage by 0.28%.
The diff coverage is 15.38%.

@@             Coverage Diff              @@
##             master     #127      +/-   ##
============================================
- Coverage     61.11%   60.83%   -0.29%     
  Complexity      172      172              
============================================
  Files            86       86              
  Lines          2083     2096      +13     
  Branches         36       37       +1     
============================================
+ Hits           1273     1275       +2     
- Misses          800      811      +11     
  Partials         10       10