Refactor PTableImpl to use Builder Pattern

Currently PTableImpl has many constructor parameters, overloaded constructors as well as overloaded versions of makePTable which basically creates a new PTable itself. Because of this, constructing new PTable instances is becoming very difficult and error-prone. We should refactor this to use the builder pattern. This will improve usability and readability of the code at the cost of some amount of code repetition due to limitations of the builder pattern itself.