Read index-pattern data from files rather than hardcoded constants

[jcantrill]

as mentioned in #48

[richm]

The kibana index-pattern data is a single line, several thousand byte JSON blob hardcoded into constant strings in the DocumentBuilder class. Instead, we should read this data from JSON or YAML files. viaq can generate the elasticsearch index templates as json or yaml files - it could also generate the corresponding kibana index-pattern data and other config data. ViaQ/elasticsearch-templates#17

[richm]

Partially addressed by #51 - if using elasticsearch index templates, kibana index patterns are not needed

[jcantrill]

Closing as will be fixed by #65