[tasklist] XML format for the configuration of visible columns

Hi developers (Tor, Trond, Serff, ...),

I have just committed the code that stores/loads configuration of the 
visible columns (width, sorting options) in/from
an XML file.

The whole implementation is now only used in the compiler submodule and 
I want to move it into the core.

see
http://tasklist.netbeans.org/source/browse/tasklist/compiler/src/org/netbeans/modules/tasklist/compiler/ 

for the source code

ColumnsConfiguration.java 
<http://tasklist.netbeans.org/source/browse/tasklist/compiler/src/org/netbeans/modules/tasklist/compiler/ColumnsConfiguration.java> 
- contains the data
ColumnsConfigurationConvertor.java 
<http://tasklist.netbeans.org/source/browse/tasklist/compiler/src/org/netbeans/modules/tasklist/compiler/ColumnsConfigurationConvertor.java> 
- converts to/from XML
CompileErrorsView.java 
<http://tasklist.netbeans.org/source/browse/tasklist/compiler/src/org/netbeans/modules/tasklist/compiler/CompileErrorsView.java> 
- methods componentDeactivated()/componentOpened()/getDefaultColumns()
columns-1_0.dtd 
<http://tasklist.netbeans.org/source/browse/tasklist/compiler/src/org/netbeans/modules/tasklist/compiler/columns-1_0.dtd> 
- DTD for the configuration
columns.xml 
<http://tasklist.netbeans.org/source/browse/tasklist/compiler/src/org/netbeans/modules/tasklist/compiler/columns.xml> 
- default columns configuration for build errors

Here is what need to be done to convert our modules to use XML for the 
configuration of columns:
- remove/rewrite TaskListView.readExternal()/writeExternal() to not 
read/write columns.
  Warning! It will be not possible to have 2 views of the same type with 
different column configuration.
- create columns.xml file for each of the existing submodules and 
integrate them using layers
- Disable reordering of the columns in TaskListView using 
getTable().getTableHeader().setReorderingAllowed(false) as I
  have not found any way to get the order of the columns in a TTV

Before I do this you have a chance to stop me or tell me what do you 
think about it.

Tim