[ephemeris] Add option for disabling the cache

[clinique]

Adds possibility to disable user defined holiday description files caching.
This in interesting especially when defining/debugging these files.
A new option can be set in the ephemeris.cfg file, cache=true/false.
Default value is true, so no breaking change if the option is absent.

[clinique]

The caching behaviour has been identified as a source of problems many times in the forum.
Current workaround being to rename the file for every modification.

[openhab-bot]

This pull request has been mentioned on openHAB Community. There might be relevant details there:

https://community.openhab.org/t/updated-custom-ephemeris-file-required-openhab-restart-to-be-effectivein/160535/3

[wborn]

It would be nicer if it would monitor changes to the file instead (e.g. using the WatchService) and then update the cached configuration.

[clinique]

That was my first thought but I though this could be a first easy step. I blocked myself because ephemeris does not have a dedicated folder for user defined files, so they can be anywhere but I'll have a look at WatchService also.

[kaikreuzer]

@clinique Could you please have a look at the failing tests?

[kaikreuzer]

@clinique Any idea why the tests keep failing? It seems unrelated, but it is still failing, even after retriggering.