Parameter can have value between tags

Until now there was only the possiblity to add a value for a parameter
using the value attribute. This had the disadvantage of not allowing
the preservation of some special characters such as newlines.

The solution to this problem is to enclose the value between a pair
of tags of the same type: e.g. <parameter name="metallic">15</parameter>.

This is particularly useful in the case of disney expressions.

Signed-off-by: Marius Avram <marius.avram1309@gmail.com>
Merge pull request #484 from marius-avram/parameter_change2

Parameter can have value between tags
fixed compilation in debug mode, plus minor code tweaks.
Fixed compile errors in debug mode
Split OIIO and OSL code paths. OIIO Texture system improvements.
Merge remote-tracking branch 'upstream/master' into est
Merge pull request #485 from est77/est

Split OIIO and OSL code paths. OIIO Texture system improvements.
Merge branch 'master' of github.com:appleseedhq/appleseed
tweaked travis build: changed git tag to travis-build, enabled verbose mode for unit tests, fixed a typo.
fixed travis build: the git tag must contain a version number of the form <major>.<minor>.<patch>.
fixed and refactored the interface and implementation of foundation::XMLElement.
Commit for curve uv computation logic
fixed a travis build error wrto access the base class variable
Merge pull request #486 from sriravic/branch_curve_03_pr

Commit for curve uv computation logic
Merge remote-tracking branch 'upstream/master' into branch_curve_03

Conflicts:
	src/appleseed/foundation/math/beziercurve.h
	src/appleseed/foundation/meta/tests/test_beziercurve.cpp
	src/appleseed/renderer/kernel/shading/shadingpoint.h
Added code to presplit curves by using a presplit parameter value in the scene file