fix profiling/LotkaVolterra.vpz model

The name of the package for the dynamic used was wrong.

(cherry picked from commit cf4e8d04d3f5e3f9f41bee60745ec4eca878d8cf)
all: fix string comparison in CMakeLists.txt

Keyword EQUAL was used to check the CMAKE_BUILD_TYPE value and that did not
work. It is now replaced by STREQUAL.

(cherry picked from commit 89b2c22547b61b2adce4883cd3fa2cb1a567f60c)
differential-equation: add output_period parameter

Output of variables was performed at each time step of integration.
To reduce the number of outputs, the parameter output_period (default to 1)
allows to perform outputs every output_period integration steps.

(cherry picked from commit 78f5a2594cc00083c654c3bae7db29905b0c83b0)
diff-equ: remove PDF from source tree

(cherry picked from commit 3c73883cf3327f4efa44204a048783e0de527838)
diff-equ: add vle.output in build depends

(cherry picked from commit b5ea5cba98959179e855878a9fe7b5914415a42f)

Conflicts:
	vle.extension.differential-equation/Description.txt