Remove Mutable classes in the objectivec wrappers.

[Paolo Brandoli]

The objective-c wrappers still have mutable and immutable class, which should be merged together.

[Paolo Brandoli]

Addresses #359. Removed all Mutable classes from objective-c code

→ <<cset c95a592f5f60>>

[Paolo Brandoli]

Addresses #359. Corrected documentation for DicomheroOverlay class.

→ <<cset 49eccab789e9>>

[Paolo Brandoli]

Addresses #359. Updated changes log.

→ <<cset 8a2d5c31b18c>>

[Paolo Brandoli]

Resolves #359 (Remove mutable classes from objective-c code) as per SOP DEVENH/2

→ <<cset 93bcb63ba4b6>>

[Paolo Brandoli]

Opening 6.0.0.0 Closes #159, #290, #326, #339, #340, #347, #350, #355, #357, #358, #359, #360, #361, #362, #363, #364, #366, #367, #368, #369, #370, #371, #372

→ <<cset 41c6182f3c2d>>