JIRA INFRA-1669 #action In Progress

- switch to server side processing to retrieve network hosts
  (the table started to be bigger and takes time to load)
- add full text search using elasticsearch

Note that only the first IP is displayed in the host table (all
interfaces were displayed before). Search can be performed on any
interfaces.

JIRA INFRA-595 #action In Progress

Use inheritance to avoid duplication

cellspacing="0" : to avoid double lines in the header
width="100%" : to have extra fields (search, paging...) aligned properly with
the table

Use endpoint argument to avoid collision with flask-admin Network

main blueprint splitted in:
- inventory
- networks