fixes #3955 - added param_true? and snippet_if_exist template methods

(cherry picked from commit 3701a8d1c6d698ea8c57321eed2f87c74bd57728)

fixes #3828 - set language locale for API messages and error responses

(cherry picked from commit 5a864bedb5d9bbbb68788169aa0f0396a312ac16)

fixes #3826: no more sql errors when trying to search for environments (also domains, operatingsystems, and models)

(cherry picked from commit 145db8634df9fbc3ffb51b80093809c5aecd0f6e)

fixes #3925 - create apipie param_groups for API v2 to DRY documentation

(cherry picked from commit 2be84f3d773e74b5cc37841284ec216996fd0b51)

fixes #3920 - prevent 500 ScopedSearch errors on the API, raise UI errors correctly

(cherry picked from commit f9bc5a8e5934aac9bd8d5488f84717d33e359501)

fixes #359 - hostname spoofing for unattended installation templates

(cherry picked from commit 5b70f0e0232bff3e580923f485bc0bd1816d9279)

fixes #3760 - API v2 define metadata @total for each controller

(cherry picked from commit 6f9438866488180e196ff18e1372cf0773afe7b9)

Conflicts:
foreman.spec

fixes #4023 - API v2 - compute resources partials should should attribute alias names and not database column names

(cherry picked from commit 8a0ffcfaa900079d628253ee7f9de2feec182914)

fixes #3998 - API v2 error on /api/compute_resources, missing gce.json.rabl

(cherry picked from commit 9926d4d3f87e439d2eaa36f5d54b07d71c57c3fe)

fixes #4132 - helper select_f missing option for :multiple => true to increase width

(cherry picked from commit 52667febe83f247b9a166c233a9bde1f62f72607)