[MERGE] SourceLayout: src/adaptation, take 1

SourceLayout: adaptation/{icap,ecap}, take 1

Moved src/ICAP into src/adaptation/icap.
Moved src/eCAP into src/adaptation/ecap.

Renamed ICAP source files from ICAPFoo.{cc,h} to Foo.{cc,h}.

Placed ICAP names into Adaptation::Icap namespace, renaming ICAPFoo to
Adaptation::Icap::Foo.
------------------------------

I am posting this for review and to provide context for the following
question.

Before ICAP and eCAP directories were moved into adaptation/, we had
Adaptation and Ecap namespaces. We now have

        Adaptation
        Ecap
        Adaptation::Icap

This intermediate state is inconsistent. What should I implement as the
final set of namespaces? The choices are

A) Flat: Adaptation, Ecap, Icap
   This option makes most adaptation names "shorter".

B) Scoped or nested: Adaptation, Adaptation::Icap, Adaptation::Ecap.
   This option better reflects the nested directory structure and scope.

When answering this question, please keep in mind that we will
eventually face similar questions when polishing authentication and
storage code:
        Auth, Auth::Basic, Auth::Negotiate versus Auth, Basic, Negotiate
        Fs, Fs::Diskd, Fs::Coss versus Fs, Diskd, Coss

I tend to favor (B). What do you think?

Thank you,

Alex.