Extensive Path Workbench improvements.

Implement libarea improvements for profile
Implement libarea pocketing.
consolidate occ and libarea pocketing operation into one with algorithm
switch
consolidate occ aand libarea profile op into one with algorithm switch
add basic engraving operation.
Add rough UI for profile holding tags
implement holding tags for libarea profile.
implement basic defaults for depth settings.
First move in Drilling is rapid to clearance height.

UI needs lots of work but is usable.

src/Mod/Path/PathScripts/nc/hpgl3d_read.py

@@ -0,0 +1,45 @@
+import num_reader
+import sys
+import math
+
+class Parser(num_reader.NumReader):
+
+    def __init__(self, writer):
+        num_reader.NumReader.__init__(self, writer)
+        self.x = 0
+        self.y = 0
+        self.z = 10000
+        self.f = 0
+        self.units_to_mm = 0.01
+
+    def ParseV(self):
+        self.line_index = self.line_index + 1
+        f = self.get_number()
+        if len(f) > 0:
+            self.f = float(f)
+            self.add_word("prep")
+
+    def ParseZ(self):
+        self.line_index = self.line_index + 1
+        x = self.get_number()
+        if len(x) > 0:
+            y = self.get_number()
+            if len(y) > 0:
+                z = self.get_number()
+                if len(z) > 0:
+                    if self.f > 40: color = "rapid"
+                    else: color = "feed"
+                    self.add_word(color)
+                    self.writer.begin_path(color)
+                    self.writer.add_line(int(x) * self.units_to_mm, int(y) * self.units_to_mm, int(z) * self.units_to_mm)
+                    self.writer.end_path()
+                    self.x = int(x)
+                    self.y = int(y)
+                    self.z = int(z)
+
+    def ParseFromFirstLetter(self, c):
+        if c == 'Z':
+            self.ParseZ()
+        elif c == 'V':
+            self.ParseV()
+