Webbrowser: visualize links on canvas (experiment)

This feature is called "Trailblazing"

For this to work you must ensure that the (URL topic's) URL ends with a / in case it points to a directory, e.g. www.deepamehta.de/

Furthermore:
Adapt File plugin's proxy service to DM4.
Accessible via /proxy (formerly /resource).

Note: The proxy service is required for the "Trailblazing" feature to work because of the browser's security restrictions.
Merge branch 'master' into trailblazing

Conflicts:
	pom.xml
4.0.3 Release
Webclient: fetch association optimization

When an association is clicked the 2 topics are retrieved *without* their composite value.

REST client: add "fetch_composite" parameter to the get_topic_by_id() method
Begin of feature "Local file management" (#78)

Adapt "Files" plugin to DM4 (begin).
Proxy feature functional.

Merged Trailblazer branch.
The Trailblazer feature is switched off.
Use the TRAILBLAZER_FEATURE switch to activate it.
See webpage_renderer.js of module deepamehta-webbrowser.

See ticket 78.
Core/Webclient fix: Data type "Number" (#80).

Number fields work now.

One issue remains: for aggregated number types no combobox is rendered.

See ticket #80
Update POMs to deepamehta-core 4.0.4-SNAPSHOT
About box: update version number (#81).

Close ticket 81.
Files module: basically functional (#78)

Functionality like in DM3: Drop a bunch of files and folders from your filebrowser to the DM canvas. They are now represented as topics (of type "File" resp. "Folder").

There are 2 features:

1) to open the file in its original application doubleclick the file topic.

2) to display the file contents right in DM's content panel click the file topic.
This is currently supported for:
- Plain text
- Images
- Audio
- Video
- PDF

It should work with Firefox and Safari (Chrome not yet supported).
Audio/Video/PDF capabilities rely on your browser plugins. Certainly there is e.g. a Firefox PDF plugin for your OS available on the net.

IMPORTANT for Firefox: for the DM file handling capability to work you must set one particular preference. Type about:config in the Firefox address bar, then double-click the signed.applets.codebase_principal_support preference to set it to true (no Firefox restart required). Later on, when you drop a file to the canvas Firefox will ask you for permission to read the file. Click "Allow".
(If you not set the particular preference, or if you click "Deny", Firefox has no access to your local files for security reasons.)
This is only a workaround. Later versions of DM will not require this setting.

With Safari no extra setup is required.

See ticket 78.
Webclient: fix a canvas bug.

Topic coordinates must be rounded to integer (sometimes they are float).
Otherwise the Topicmaps REST resource methods do not match (-> 404).
Webclient: support for boolean fields (#82)

See ticket 82.
Begin of Icon Picker module (#84)

Currently not working (endless recursion!)

See ticket 49, 82, 84.
Core: fix endless recursion

... that occured when "View Configuration"'s child types have a view configuration itself.
Runtime: add "exec" to deepamehta-linux.sh (#83)

Close ticket 83.
Iconpicker: basically functional (#84)

See ticket #84.
Iconpicker: layout (#84)

Furthermore in Weblient module: revise and simplify RenderHelper code.

See ticket 84.
Webclient: change view config model.

"Icon Source" is aggregated (instead composed).

Adapt Icon Picker module.

Rename topic type "Icon Source" -> "Icon"
(dm4.webclient.icon_src -> dm4.webclient.icon)

Adapt modules.

Webclient: add some icons for the user to play with.
Core: change updateTopic() service call.

It returns Directives (instead a Topic).
Add directive UPDATE_TOPIC.

Applies to the REST API as well (PUT /core/topic).

Adapt deepamehta-webclient module.
Core: POST_UPDATE_TOPIC hook is functional.

Webclient: uses this hook to update the cached view configuration once a view configuration is updated in the DB.
Core: extend POST_UPDATE_TOPIC hook

... by a "Directives" parameter.

Webclient: update model and GUI once a view configuration is updated.