Support reloading a floating license if number of tester/execution is equal or bigger

The floating license files which are needed to run the license server can expire. It would be nice to enable the customer to replace the current file with an equivalent file with extended lifetime (later issue date, maybe different longevity). Use the signal SIGHUP (and Windows equivalent) to make the server reload the license file.

Requirements

The server should not have to disconnect clients because the terms of the license have new restrictions that were not present in the old license. These requirements ensure that there is no need to disconnect currently active license holders:

• The newly loaded license must be valid
• Issue date and longevity may differ
• The "new" issue date can be older than the "old" issue date, however the license must still be valid
• The number of available licenses for tester/execution slots is >= existing amount
• All Squish editions licensed in the old key must also be present in the new key