[NEXUS-6045] drop CacheControl, all impl of WebResource had this, just make it part of the WebResource api,
Changed WebResource.getLastModified() to return long (instead of Long), it was being misused anyways if this was ever null it would have puked,
Use URLConnection.getContentLengthLong(),
Drop more unused static bits from restlet plugin,
Unwire licensing resources from NexusApplication since they are pointless now,
Drop NexusApplicationCustomizer, not used by us anymore and any users who may have been using it will have to rewrite to be functional again anyways,
Simplify servlet module/names
Replaced plexus resources with web-resources to render licensing/{request|activate}.html and moved back to /licensing
Added BaseUrlHolder, and initial hook up to WebResourcesServlet to expose the baseUrl generally to components
simplify message
Configure security and some core filters in CoreModule (including a new BaseUrlHolderFilter)
Dev resources removal, leak fixes.

Changes:
* removed unused DevModeResourceFinder
* removed DevModeResources stuff from static
  resource imples, as those are now handled by WebResourcesServlet
* fixed leak detected by some tools, as URLConnection were left
  "dangling" without being closed (but they were asked for last mod
  time and such only, since client got them cached already)
Reusing baseUrl from holder.
fixed templates now that nexusUrl does not have trailing "/" anymore
replaced more places that needed baseUrl with BaseUrlHolder.get()
dropped code that was stripping off "/" its no longer needed.
moved calc of the url from webutils to filter, code should only be used here
dropped pointless url arg from IndexPageRenderer.render()
DefaultWebResource -> UrlWebResource
more comments about removing some manual resource shit which is just added overhead now
Allow standalone WebResource components to be discovered.
remove redirect to index.html, render index by default like most other web servers in the world do
Remove appRootUrl bits from store request and request content, these were seemlying only used to access same data from BaseUrlHolder.
change logging order
Merge branch 'master' into even-more-webresource-cleanup
deprecate getContextRoot() for clarity so usage pops out more in IDE tooling
Use BaseUrlHolder instead of getContextRoot()
Add ErrorPageFilter to CoreModule, this still won't catch for restlet1x but that stuff will be going away.
Note error-page stuff in restlet.
Expose cause to template as Throwable.
Use 0x70000000 to bind the high-level filters instead of MAX_VALUE to allow some room if/when needed.
ErrorStatusServletException.getRootCause() and notes about not using ServletException as super.
Add ErrorPageFilter to CoreModule, this still won't catch for restlet1x but that stuff will be going away.
Note error-page stuff in restlet.
Expose cause to template as Throwable.
Use 0x70000000 to bind the high-level filters instead of MAX_VALUE to allow some room if/when needed.
ErrorStatusServletException.getRootCause() and notes about not using ServletException as super.
normalize @since
buffer file i/o
Drop pointless empty map for attributes on ContentServlet PUT
ErrorStatusException back to using ServletException as super-class, for some reason its not working as RTE (no big deal).
Move FileWebResource to nexus-plugin-api for parity with UrlWebResource.
Normalization, formatting and tidy.
simplify