Add option to allow changing mutable and static variables

[TheMostDiligent]

Proposed API:
Add SET_SHADER_RESOURCE_FLAGS enum

enum SET_SHADER_RESOURCE_FLAGS
{
    SET_SHADER_RESOURCE_FLAG_NONE = 0,

    SET_SHADER_RESOURCE_FLAG_UNSYNCHRONIZED = 1u << 0
};

Add new flags member to IShaderResourceVariable::Set and IShaderResourceVariable::SetArray methods.

Update error messages to report unsyncrhonized set variable errors and suggest using flag SET_SHADER_RESOURCE_FLAG_UNSYNCHRONIZED.

Update documentation here and here.