added ServicesTypePrefix property in RuntimeTypeModel.CompilerOptions (#1184)

[MFinkBK]

this lets you override the <Service> prefix for the generated serializer services class

fixes: #1184

[mgravell]

I think I'm fine with this, but I wonder if we should do something simpler and just change the default to ___PBN_Services___ or similar, which should be perfectly fine, while being suitably unlikely to collide?

[MFinkBK]

I'm fine with either change, but I didn't know if the <Service> prefix has any other meaning (than unreferenceable from C# code maybe?). If you want, I can modify the PR.

[mgravell]

It has no significance other than being known to be non-conflicting, by being "unpronounceable"; but something like the above should be fine in all reasonable scenarios, without complicating the public API

[MFinkBK]

I reverted my change and just use the prefix you suggested. Just tell me if I should squash the commits into a single commit

[MFinkBK]

I'm sorry about the whitespace noise

[mgravell]

Should be on myget shortly. Thanks for the input!