This change should make sure that only those settings actually make it into config.yaml
per plugin that do differ from the default settings. Up until now the full dictionary as received
e.g. from the REST API was saved, regardless whether it contained (only) default values or not.
That led to a lot of "null" entries in the config.yaml file, which for one looked horrible and also
led to problems when a plugin actually wanted to change its default values.
With this commit, two things are done. One, upon saving a configuration the default
implementation of the save routine in the settings plugin now first diffs the new data against
the defaults and only saves what is different. Two, upon server startup a cleanup method is
now called on settings plugins whose default implementation fetches the current data stored
in config.yaml, diffs that against the defaults and only writes back the diff result. If that is empty
the entry is completely deleted from config.yaml.
We now wait until the settings have been saved before we close the dialog.
That should hopefully reduce chances of an asynchronous "Oh no, the settings
were updated" message showing up just when finishing the dialog.
At least if necessary (added new boolean flag to the constructor of
LargeResponseHandler for that). While at it also rename UrlForwardHandler
to UrlProxyHandler (it does not forward, it proxies) and make it aware of
ETag and Expires headers.
Bit of a debate with some gcode purists. RepRapPro demands an S
parameter. Adding S255 should be backward compatible with the firmwares
that recognize M106 as full on. As with other issues, it'd be nice to
have something more to go on here than the reprap wiki and firmware
source code.
ETag values returned with download responses were cached internally within
the LargeResponseHandler class, with the file's path as key. That let to
problems once the content changed and hence the ETag value actually
becoming invalid. Since the path however stayed the same, the same ETag
value for the modified file was assumed and a 304 Not Modified response
was generated.
This patch changes the behaviour of LargeResponseHandler to use
the last modified date of the file as the ETag value and alternatively allowing
an etag generator function to be provided as constructor parameter as well
to use for calculating (or disabling) the ETag header dependant on the
situation.
