This pull request includes several changes aimed at improving the codebase by ensuring consistency in the use of toIndexedSeq and toSeq methods, along with some minor refactoring. The most important changes include updates to the GraphFrame class and related objects, as well as updates to other classes and objects within the graphframes package.

Improvements to GraphFrame class and related objects:

• src/main/scala/org/graphframes/GraphFrame.scala: Modified the toString method to use toIndexedSeq and toSeq for column selection consistency.
• src/main/scala/org/graphframes/GraphFrame.scala: Updated fromEdges method to use distinct() instead of distinct.
• src/main/scala/org/graphframes/GraphFrame.scala: Updated colStar and nestAsCol methods to use toIndexedSeq and toSeq respectively. [1] [2]

Refactoring in other classes and objects:

• src/main/scala/org/graphframes/examples/BeliefPropagation.scala: Ensured consistent use of toInt conversion after count() method in runBPwithGraphX and runBPwithGraphFrames methods. [1] [2]
• src/main/scala/org/graphframes/examples/Graphs.scala: Updated ALSSyntheticData method to use toIndexedSeq for data and vertices.
• src/main/scala/org/graphframes/lib/BFS.scala: Modified paths.select to use toSeq for column selection.
• src/main/scala/org/graphframes/lib/GraphXConversions.scala: Updated select method to use toSeq for field selection.
• src/main/scala/org/graphframes/lib/ShortestPaths.scala: Replaced scala.collection.JavaConverters with scala.jdk.CollectionConverters.
• src/main/scala/org/graphframes/lib/ShortestPaths.scala: Updated select method to use toSeq for column selection.
• src/main/scala/org/graphframes/lib/TriangleCount.scala: Modified select method to use toSeq for column selection.

This removes warnings when we build. Note we can't use WrappedArray if we will have support for Scala 2.12