fix printing for evaluation level and make fr show the current level by default instead of level 1

[KristofferC]

Fixes half of #140. @Keno, I'm having troubles reproducing the problem with the evaluation in the wrong level. For example:

julia> function f(x)
          x = 1
          g(x)
       end
f (generic function with 1 method)

julia> function g(z)
           y = 4
           return z
       end
g (generic function with 1 method)

julia> @enter f(3)
In f(x) at REPL[24]:2
 2     x = 1
>3     g(x)
 4  end

About to run: (g)(1)
1|debug> s
In g(z) at REPL[25]:2
>2      y = 4
 3      return z
 4  end

About to run: 4
1|debug> f 2 # at frame 2
In f(x) at REPL[24]:2
 2     x = 1
>3     g(x)
 4  end

About to run: (g)(1)
2|julia> x 
1

2|debug> f 1
In g(z) at REPL[25]:2
>2      y = 4
 3      return z
 4  end

About to run: 4
1|julia> x
ERROR: UndefVarError: x not defined

[KristofferC]

I'm suprised about the output:

2|debug > fr
[2] add_constraints(b, f, s) 

Because before this PR fr (without arguments) would show for level 1 and not current level.

[codecov-io]

Codecov Report

Merging #142 into master will not change coverage.
The diff coverage is 50%.

@@           Coverage Diff           @@
##           master     #142   +/-   ##
=======================================
  Coverage   80.89%   80.89%           
=======================================
  Files           7        7           
  Lines         471      471           
=======================================
  Hits          381      381           
  Misses         90       90

Impacted Files	Coverage Δ
src/commands.jl	68.68% <0%> (ø)	⬆️
src/repl.jl	77.04% <100%> (ø)	⬆️

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[codecov-io]

Codecov Report

Merging #142 into master will decrease coverage by 0.34%.
The diff coverage is 25%.

@@            Coverage Diff             @@
##           master     #142      +/-   ##
==========================================
- Coverage   80.89%   80.54%   -0.35%     
==========================================
  Files           7        7              
  Lines         471      473       +2     
==========================================
  Hits          381      381              
- Misses         90       92       +2

Impacted Files	Coverage Δ
src/commands.jl	67.32% <0%> (-1.37%)	⬇️
src/repl.jl	77.04% <100%> (ø)	⬆️

---

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[KristofferC]

I'll blame the wrong execution in #140 on the old version used