[#3880] - improve configurability of ireport

we develop our reports w/in a source control branching structure... there are quite a few things that can be different from branch to branch... location of common report elements, our java helper ibraries jar, etc..

at run time we just pass in the correct parameter value for these things and it is no problem, but at design time it is more tricky. i find that setting default values in the report parameters is very restrictive... i.e. if i use a default value to specify location of common report elements, that location may be different from branch to branch or machine to machine.

i would like to be able to specify all of these various configurations via some type of properties file that could be located w/in the directory structure containing the report source files. one of the things that properties file could provide is the values of parameters that should be used when previewing the report ( hence a way of specifying default parameter values that will be more like what happens at runtime )

my 'inspiration' for that type of solution comes from the way our Perforce source control works.. it allows use of a .p4env properties file. if you run a p4 command from a dos prompt it searches from your current directory up the directory structure until it finds a .p4env file and then uses the settings from that file. a similar approach in ireport would be great - if i open a .jrxml it could search from the report directory back to the root and use the first relevant properties file it finds.