Refactored fabric PipeconfLoader to automatically build pipeconfs

Fabric.p4 is evolving in a way that will allow multiple profiles (e.g.
fabric, fabric-spgw, fabric-int, etc). Moreover, we need to support
multiple targets (e.g. BMv2, Tofino, etc.) as well as platforms
(variant of a target). Maintaining a pipeconf for each
profile/target/platform is time-consuming.

The new PipeconfLoader automatically builds pipeconfs based on the
available p4c compiler outputs available in the 'resources' directory.
This approach removes the need to maintain separate pipeconfs like
fabric-pro. Those interested in using fabric.p4 with targets other than
BMv2, will simply need to place the appropriate target/platform-specific
P4 compiler outputs in the resource directory.

Change-Id: I58d208a1837e747357373b2296cb950f13799ed6
diff --git a/pipelines/fabric/src/main/resources/.gitignore b/pipelines/fabric/src/main/resources/.gitignore
new file mode 100644
index 0000000..4832ef2
--- /dev/null
+++ b/pipelines/fabric/src/main/resources/.gitignore
@@ -0,0 +1 @@
+p4c-out/*/tofino