Time based policies: code cleanup.

Jira issue: WP-1144
Exporting new method (getPolicyFilename) from "pm"

Retrieve the file name passed to the pm module constructor.
Doesn't check if the file exists or if it's a well
formed policy file.
Changed Path to path

removed also some unuseful "require"

Jira issue: WP-1169
Merge pull request #43 from smonteleone/pm.cc__getPolicyFilename

Exporting new method (getPolicyFilename) from "pm"
Merge pull request #41 from steverc/WP-1144-policyTiming2

Time based policies: code cleanup.
Merge pull request #44 from smonteleone/WP-1169

Changed Path to path
Moved module shared variables inside instances.

Added also a method to check policy updates and refresh PM instances.

Jira issue: WP-1168
Merge pull request #45 from smonteleone/WP-1168

Moved module shared variables inside instances.