Add JSON input for agents

If supplied a json-file (matched by suffix .json) instead of a regular
CFEngine policy file, agents will parse the JSON and load the policy
from there.

To convert a policy file to JSON, use cf-promises --policy-output-format=json

This feature is experimental.
Merge pull request #355 from jimis/bug2193

Fix executable path for running "cf-execd --once" when bootstrapping.
Remove old svn tag and update with relevant core version
Subversion is no longer used and the current stdlib won't work with
3.1.0.
Get rid of confusing "Risk of combinatorial explosion" warning

(Redmine #2005)
Do not exclaim at the end of cf-runagent run (Redmine #2177)
Merge pull request #358 from dottedmag/cleanups/no-useless-exclamation

Do not exclaim at the end of cf-runagent run (Redmine #2177)
Merge pull request #357 from dottedmag/cleanups/allow-reports-in-universal-context

Get rid of confusing "Risk of combinatorial explosion" warning
Remove unimplemented flag -a from cf-promises
don't create a symlink in /usr/local/sbin for cf-know in Community policy. cf-hub and cf-know were removed since 3.4.0
Standardize, remove constraints.h. Moved into policy.h
Free the dup'd string.
Remove EscapeJson
Move AgentTypeToString from conversion to generic_agent
Standardize enum cfmeasurepolicy -> MeasurePolicy
Standardize enum cfenvironment_state -> EnvironmentState
Rename String2InsertMatch -> InsertMatchTypeFromString
Standardize enum cfinterval -> Interval
Standardize enum cfdbtype -> DatabaseType
Rename String2ReportLevel -> OutputLevelFromString
Standardize enum cfcomparison -> FileComparator