This adds support to push docker images to quay.io, like other projects in
the iovisor org.

It separates docker image builds into a separate github workflow, and
refactors the package building process slightly, to be generic, in order to
create builds for both ubuntu 16.04 and ubuntu 18.04.

This provides a means to distribute intermediate apt packages between releases,
and also enables uploading these as CI artifacts.

As recent releases have not annotated their tags, it drops the requirement for
tags to be annotated in selecting the version to use.

With this commit, pushes to branches can trigger tests directly on
Github Actions.

Here it will be able to test against kernel 4.14 and 5.0.0, which correspond
to the latest Ubuntu LTS kernel releases.

Tests are run for both Debug and Release modes.

Tests run inside docker, in an ubuntu 19.04 container base.

For the github workflow:

- The test_libbcc suite is run first, to potentially fail fast on these faster
unit tests.
- The Python test suite is run

Some of these tests are allowed to fail, but the failure is still reported:

- In catch2 tests, using the [!mayfail] tag, where this will be displayed in
the test summary
- In Python unittests, using the `@mayFail("Reason")` decorator, which is
introduce for consistency with catch2. These will report the reason for the
failure, and log this to an artifact of the test.

Add a new option --cgroupmap in execsnoop and opensnoop to only display
results from processes that belong to one of the cgroups whose id,
returned by bpf_get_current_cgroup_id(), is in a pinned BPF hash map.

Examples of commands:
    # opensnoop --cgroupmap /sys/fs/bpf/test01
    # execsnoop --cgroupmap /sys/fs/bpf/test01

Cgroup ids can be discovered in userspace by the system call
name_to_handle_at(); an example of C program doing that is available in
examples/cgroupid/cgroupid.c.

More complete documentation is added in docs/filtering_by_cgroups.md

The documentation is independent from Kubernetes. However, my goal is to
use this feature in Kubernetes: I am preparing to use this in Inspektor
Gadget to select specific Kubernetes pods, depending on a Kubernetes
label selector. Kubernetes pods matching the label selector can come and
go during the execution of the bcc tools; Inspektor Gadget is updating
the BPF hash map used by the bcc tools accordingly.

* inject: Add support for alloc_page family of functions

* Add vim backup files to gitignore

* Add Getting Started section in README.md
* Add a virt-install script which creates a BPF-capable Fedora 21 VM
* Fix a test that was failing on F21

Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>

Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>