Implement getAlignmentBaseline and getBaselineShift in ios. (#527)

* Implement correct transform parser

* Implement getAlignmentBaseline and getBaselineShift in ios.
Add comments to glyphcontext and align with android.
Implement correct isWordSeparator predicate.
Cleanup GlyphContext j2objc remnants.

* Fix getBaselineShift bugs and font data invalidation.

ios/Elements/RNSVGGroup.m

@@ -13,6 +13,16 @@
     GlyphContext *_glyphContext;
 }
 
+- (void)setFont:(NSDictionary*)font
+{
+    if (font == _font) {
+        return;
+    }
+
+    [self invalidate];
+    _font = font;
+}
+
 - (void)renderLayerTo:(CGContextRef)context
 {
     [self clip:context];
@@ -62,7 +72,7 @@
 
 - (void)pushGlyphContext
 {
-    [[[self getTextRoot] getGlyphContext] pushContextWithRNSVGGroup:self font:self.font];
+    [[[self getTextRoot] getGlyphContext] pushContext:self font:self.font];
 }
 
 - (void)popGlyphContext