long-term restructuring

[IndrajeetPatil]

• add sample size info to bf-related expressions
• check if a 0-parameter template can be repurposed for bf-expressions
• only support symbols, and not strings as argument inputs
• check if things work as expected with for loops
• instead of showing centrality in Bayesian template, show what the estimate actually is
• use {glue} for creating expressions
• Use rlang::parse_expr() to parse expressions