[fix] Fix loop closure bugs

Goal

Fix remaining bugs in loop closure process in library.

Changes

• Fix query/revisited bad initialization order in registration process
• Fix loop closure registration covariance
• Fix segfault due to change in keypoint type
• Add comments

Checklist

• Camel case everywhere except for ROS variables/parameters
• Lower case for local variables and lambda functions
• Upper case for members, methods and tool functions (in Utils)
• Precise namespace when calling a function (or this->X or classe.X)
• Align code (for multiline if and while, "&&" or "||" go in upper line to ensure alignement)
• Check your spaces
  • between if, while, for and parenthesis
  • between operators and variables: e.g. a + b
  • after ","
• Mind your commit titles/desc (plurals, he/she + "s", correct tags, title should begin by a verb...)
• Function names should start with a verb, variable names should start with a name
• Macros should be between {}
• Do not use negative boolean (i.e. noJoe)
• Check minimal size of the types (double -> float -> int -> uint)
• Check const and ref in functions arguments
• References should be written "type& name", not "type &name"
• Update documentation
• Add MR labels [ROS]/[ROS2]/[PV]
• If ros/ros2, update task table here
• Add a comment over each non trivial function in header files
• Add a header to each new file