[pidcat] Display package:process_name in process birth/death messages

Summary: Making sense of a birth/death message is made easier by specifying which process it applies to, and not just the component or the pid.

Test Plan: Run, monitor message lines when cycling a multi-process app, inject None as a process name to check resilience.
[pidcat] Allow package to specify a process as well …

Summary: Android apps can use multiple processes (eg, chrome), which are identified as <package_name>:<process_name> in logs. The names are defined in the manifest.
The main process is referred to as simply <package_name> by android.
Add the ability to specify a target process as part of what was until now the package name in pidcat, or all processes if no process is specified.

Usage:
 * pidcat <package_name> will match all of an app's processes (catchall).
 * pidcat <package_name>:<process_name> will match a given named process.
 ** In particular, pidcat <package_name>: will ensure only the app's main/default process is matched.

Test Plan: Run the script, try out with no process, empty (aka default) process, named process. Try multiple entries.
Fixed adb path hint in readme
Updated text pointing to path to adb in readme
Merge pull request #52 from dfuerniss/master

Fixed path to adb in Readme
Merge pull request #50 from LouisBVL/process_output

Display package:process_name in process birth/death messages
Merge pull request #51 from LouisBVL/process_parse

Allow package to specify a process as well …