extras: Initialize work file descriptors in FileDescriptorActivity

The work FD's didn't have initial values, and so if isUpdated() is
called before the activity starts it's loop() then junk values are
returned.

This zeroes the work FD's during construction.
extras: Log an error if a FileDescriptorActivity fails to start

The error simply occurs silently otherwise.
extras: Support microsecond timeouts in FileDescriptorActivity

Use microsecond instead of millisecond timeouts. Adds new get/set
operations that explicitly deal with microsecond level timeouts,
while leaving the existing millisecond get/set timeout operations.

Setting a negative timeout is now checked for and prevented.
extras: Support pinning a FileDescriptorActivity to a CPU mask
extras: Support an intended period in FileDescriptorActivity

A component querying a FileDescriptorActivity (FDA) will always
receive back a period=0. This may be invalid if the FDA is actually
tracking a periodic signal, e.g. say a sync signal from hardware. In
this case there is a period at deployment time that the component
is intended to run at, but this is not available to the underlying
component.

This adds an intended period and returns that as the period of this
activity. The default intended period is the same as the actual
period=0. The actual period remains the same; 0.
ServiceRequesters are managed by shared pointers

* Use shared pointers to manage ServiceRequester instances internally, like for Services.
* Added a ServiceRequester::addServiceRequester(shared_ptr) member function to add service
  requesters created elsewhere to the interface (in analogy to Service::addService()).
* Make ServiceRequester::connectTo() a virtual function so that implementations can
  override it (e.g. to connect ports).

This commit breaks the ServiceRequester API and needs patches in ocl and rtt_roscomm.

Signed-off-by: Johannes Meyer <johannes@intermodalics.eu>
Merge branch 'file-descriptor-activity-fixes' of gitorious.org:orocos-toolchain/snrkiwi-rtt into HEAD
Merge branch 'servicerequester-refactoring-2' of https://github.com/meyerj/rtt into HEAD